Insight 2005 – Minneapolis 9-13th October 2005

Diapers to 2025
Carlos Richer of Richer Investments said the diaper industry is in very bad shape. He argued that we are in the middle of a 7-11 year “purging cycle” which forces the closure of the inefficient, and drives the remaining smaller players to network with suppliers and retailers in order to better manage the proliferation of diaper types (SKU's). These purging cycles (aka global price wars) are triggered by supply chain problems, and this time it's the oil crisis and its effects on SAP price and availability. However by 2025 the following could be expected:

• Global diaper use would double as the number of users would increase from 1 in 5 today to 1 in 3. (Diaper use per baby would decline by 5% due to less frequent changing. The number of babies will increase only marginally)
• Compared with the 10 million babies in the USA , India (61 million) and China (42 million) had the largest population of 0-30 month-olds.
• While the % babies in the US population would increase slightly by 2025, the Indian and Chinese percentages would decrease slightly.

Using pre-segmented purchasing power parity (PPP) and knowing the minimum disposable income needed to trigger purchases of disposable absorbents, Dr Richer had also calculated the likely penetration of disposables by country. Full details were on his website www.richernet.com , where adjustments had been made to allow for unemployment levels (source of low-cost maids to wash diapers) and cultural resistance (Chinese reluctance to use diapers of any kind). The method suggested that India should now have 2% of changes on disposables, with China at 5.5%, Indonesia 9%, Brazil 30%, Mexico 59% and the USA 96%. There were other issues to consider when trying to assess growth potential. For instance, very uneven distribution meant that Brazil , Mexico and Russia would grow much more slowly than implied by the size of the unpenetrated market. In China , modern advertising could be expected to overcome the cultural resistance in the near future, leading to explosive growth of diaper sales. India would follow in 3-5 years time and will become the world's largest diaper consumer by 2025. North Africa also showed exceptional growth potential using this method.

Diaper design could be expected to evolve:

• To address the most important unmet-need: fewer changes/day.
• Desalination of urine by coverstock or ADL would increase the SAP's capacity.
• To dewater the SAP after disposal, microencapsulated salt would be added which would be released as the capsule dissolved in landfill.
• Microcapsules could be used in the coverstock to release buffers if the skin pH got too high.
• They would be compressed more highly to reduce volume in shipping and storage.
• Highly breathable nonwoven backsheets would be self-sealing, eliminating the need for film lamination.
• More elastic diapers would further reduce leakage (and reduce SKU's?)
• Air-laid preformed cores would be used.
• Pulp companies would move into diaper production in the emerging markets, but diaper companies would not integrate backwards to pulp products.

The adult incontinence market looked more attractive. The global population of over-70's would grow from 316 million today to 563 million by 2025 and with the expected increase in prosperity, the market for adult diapers would grow three or fourfold. China (62 million over 70's growing to 130 million) and India (32 million growing to 65 million) would lead this growth. There would be little growth in Europe which was already “old” in population terms.

In response to questions, cheaper to use two-piece diapers would lead the penetration of underdeveloped markets (J&J mentioned as active in this area). The SAP price/availability problem is temporary and will correct itself. China will sort out its intellectual property issues and start producing diapers. They are looking at exporting highly compressed diapers to Europe .

PP Supply Problems

Bob Dennett, CMAI North America's Director of Polypropylene pointed out that since hurricanes Katrina and Rita, several refineries had shut down, feedstocks were limited, there was a hydrogen shortage and inventories were tight. The result: propylene from the refining industry would soon go above 50 c/lb for the first time. Quite apart from the short-term problems, demand for propylene, once a no-value by-product of ethylene production, was now exceeding the demand for ethylene and gasoline. 53% of the propylene produced in the USA in 2004 went to PP production. Alternative propylene technologies, such as propane dehydrogenation did not exist in the USA but were becoming a source in Europe . Metathesis i.e. ethylene + butylene à 2 propylene, was being developed mainly in Asia .

Global demand is expected to grow by 5% pa reaching 82 million tonnes by 2010. Of the additional 20 million tonnes needed by then, 2/3rds is expected to come from stretching existing capacity and the rest from new installations.

Propylene price is expected to peak in 2006 at about $900/tonne and then decline to ~$550/tonne as the new capacity comes on stream.

Polypropylene is now the largest selling polymer (24%) having taken the lead from PVC (19%). The polyethylenes follow with High Density (17%) Low Density (11%) and Linear Low Density (11%) Polyester and Polystyrene have 7% each. 2004 PP demand was 38.6 million tonnes and 16% of this went to fibers. The preferred pricing is in cents per cubic inch, which emphasises the advantage over the denser polyester. (PP=1.5 c/ci compared with PET 3c/ci.). The main expansion of PP production will be in the Middle East and North Africa, but this is unlikely to be economically exportable to the USA .

Polypropylene resin price is expected to peak in 2006 at around 70 c/lb and then decline to 40 c/lb by 2010. These prices are for general purpose high pressure injection moulding grade.

PET Price to Fall?

Ian Julian, also of CMAI gave the polyester section of the talk he presented to INTC – St Louis last month, adapted to take account of the Katrina and Rita effects. Almost 25% of the ethylene glycol capacity and over 12% of the paraxylene capacity in the USA was taken out by Katrina. The halt in oil production in the Gulf of Mexico compounded the matter. Chemical intermediate prices and hence polyester prices all ride on crude oil price, and while the hurricanes mean that the “highs” will be a little higher, the following “lows” will be even lower. He expects the increased imports into the USA which are now occurring to take advantage of the higher prices will overrun demand and lead to a polyester price collapse. However the shortages will lead to some substitution of polyester by other polymers and not all of this market loss will be regained as the prices fall.

SAP Availability

Blake Kuster of Absorbent Technologies Inc reviewed the factors affecting the current SAP price/availability problems. The buyers market had gone and shortages, allocations and rising prices were the order of the day.

• 1.3 million tonnes of SAP capacity (nameplate) were in place, 38% in Asia, 35% in the USA and 27% in the EU.
• BASF is the leading producer with 24% share, followed by Degussa (21%), Nippon Shokubai (20%), Dow Chemical (11%) and San Dia (10%).
• Supply will grow by 8% in 2005 as two new Chinese plants come on stream, but this is still insufficient to meet demand.
• A further 5-6% pa demand growth is expected through 2008 but supply will grow by this level only in Asia and Europe . The US installations will be modernizations with no increase in output.
• SAP is made from acrylic acid, which in turn depends on propylene. Demand for glacial acrylic means that this is currently selling at prices higher than those available in the SAP market, which consumes about 25% of the 4 million tonnes of GAA.
• 70% of the new AA capacity is going into China who now make 7% of the global needs.
• With AA prices up 30% to $2400/tonne, there is no incentive to sell to SAP producers.

Why is AA becoming scarce and expensive? Because of higher demand than anticipated in the emerging markets, and higher usage in the increasingly popular water-based paints.

Propylene, a by-product of ethylene production, is the raw material for the polypropylene (60%) and the SAP (1%, via AA) needed in diapers. Here too demand is exceeding supply and propylene prices have doubled since 2002 (to $1000/tonne). Asked when the market would get back into balance Mr Kuster felt supplies would be tight through 2008 and further out it depends on how propylene production can be expanded. How should the nonwovens industry respond? Lock in your suppliers, multi-source and be prepared to change in the turbulent times ahead! Could more fluff be used? Yes but even that is in high demand especially in emerging markets. Could CMC's or crosslinked starches be used to make SAP's? Yes but they did not have the production capacity to fill the emerging gap. Concluding, Mr Kuster felt there could soon be a paradigm shift in absorbent product design.

Extending SAPs

Shuojia Dong of Groupe Lysac Inc. reported the development of starch-based superabsorbents specifically to blend with the increasingly expensive oil-based product on which most of the absorbent products industry now depends. Lysorb 220 was initially developed to blend with SAP to allow products to meet the Nordic Ecolabelling requirement of a minimum level of renewable materials and a maximum level of residual monomers and extractibles. Actyfill 20 , a glass-like starch gelatinized by extrusion, was then developed to blend easily with SAP at levels up to 20%, to reduce costs without affecting performance. This is now commercial and the next generation, Active Filler 2 offers greater cost savings by incorporating 26 to 60% of cheap naturally absorbent inorganic powders. Here some losses of performance (Free swell, centrifuge retention and absorbency under load) are observed at the 20% blend level with SAP. So, Active Filler 3 is under development, and this has the same composition as Active Filler 2 but uses a different extrusion process to boost absorbency and porosity. This has been tested in blends of up to 40% with SAP. Total acquisition times are slightly less than those of SAP either at normal loading or at 60% normal loading (with fluff pulp as the missing 40%). Total rewets were 0.2 gms for the 100% SAP, 5.9 gms for the 60% SAP loading, and 1.0 gms for the 60% SAP with 40% Active Filler 3 .

In response to questions:

• Lysac's capacity for Actyfill is about 35,000 tonnes/year
• Cost? “It is less expensive than the majority of SAP's”
• Could it be used above 40% blend? Maybe
• There are no IP issues with the process – Lysac have “right to practice”
• The materials are FDA approved.
• Their market share is increasing.

Low SAP diapers

Mark Bolyen of Marketing Technology Services considered how diapers may be redesigned to use less of the increasingly expensive SAP. SAP prices bottomed out at about 65 c/lb in 2002 and since then had risen to over $1.10. Pulp prices, currently around $600/tonne, cycled between 500 and 1000 $/tonne. Using MTS's large database of diaper construction data Mr Bolyen has modeled the P&G Pampers and KC Huggies diapers to examine the effects of various core compositions on cost and performance. From the bewildering mass of results it appeared that using July 2005 prices P&G had scope to reduce SAP by 10% and increase pulp by 21% to yield a cost saving of about $1.10 per 1000 diapers without sacrificing much performance. K-C would save about $1.20 /1000 from the same change but would suffer more of a performance loss because their diaper already used less SAP than P&G's. Leakage performance could be maintained at even lower SAP levels if the elastication levels were increased to get better fit. However this would cost more. Reducing SAP content by localising it in the target area would be worthwhile.

Superabsorbent Fleece

Samantha Champ of BASF AG ( Germany ) described their work on Luquafleece, made by solution polymerization of a partially neutralized acrylic acid on the surface of the fibers of a nonwoven. A mixture of the monomer, cross linkers and initiator is sprayed onto a high-loft polyester nonwoven, polymerized and dried through an oven. The SAP appears as ~300 micron beads attached to the fibers of the fleece, one example having 200 gsm applied to each surface. The statement “50-500 gsm SAP can be applied to fleeces weighing more than 70 gsm” indicated 1 to 1 loadings of SAP on fiber ought to be possible. The shape of the beads on the fiber can be controlled by varying its wettability; hydrophilic finishes allowing the SAP to encapsulate the fibers in oblong blobs, while hydrophobics give spherical blobs. Silicone finishes give spherical blobs sitting on the surface and unattached to the fibers. The fleece with 400 gsm of SAP gives a saline free-swell of 18 g/g (7 liters per square metre) and centrifuge retention of 12 g/g (5 lsm). In addition to the currently commercial hygiene applications, the fact that it outperforms silica gel allows it to compete in climate control and several other applications:

• Packaging climate control.
• Food packing soaker mats.
• Horticultural watering mats - liners for hanging baskets.
• Chair seats and mattresses to achieve extra comfort.
• Filters to keep non-aqueous liquids dry.

Compared to silica gel, the Luquafleece releases the moisture faster when the humidity drops.

In response to questions, Ms Champ admitted that the saturated SAP is relatively easy to squeeze out of the fleece. The process of manufacture was specialized and she could not recommend in-situ polymerization on nonwovens production lines. The beads do have a core-shell structure. Luquafleece has been commercial in the EU for 2 years and the production capacity is fully utilised.

Sonic Bonding for diapers

Torsten Brieger of Hermann Ultrasonics explained that adhesives and synthetic rubbers are based on isoprene, and the demand for isoprene is now unexpectedly high after a period of low prices and no investment. Isoprene comes from oil via the steam cracker as a by-product of ethylene manufacture, so the supply side is suffering also. Production actually declined in the first half of 2005 and shortages are expected to continue for some time. Allocation is inevitable, and new adhesives take a long time to qualify.

Sonic bonding allows adhesive-free assembly of hygiene products and the latest generation of machines with micro-gap control can produce consistently high-quality bonds at 500 metres/minute. It is now being developed to:

• Laminate the components of the cloth-like backsheets
• Attach the leg cuffs and the closure tapes
• Attach the elastic waist band and the frontal tape landing zone.
• Spot weld the acquisition distribution layer.

Micro-gap control, achieved by a stepper motor operating in 0.3 micron steps is the key to consistent operation at high speeds. It cannot compensate for variations in the number of layers to be bonded or the thickness of the nonwoven.

Powder Bonding Perfected

Christian Haas of Strahm Textile Systems AG ( Germany ) described the use of a 10-50 kV field alternating at 50-60 Hz to encourage polymer particles to distribute themselves uniformly through the thickness of a high-loft web. The non-conductive powder must be applied to the upper surface of the non-conductive web prior to entering the electric field, and the particles must be smaller than the pore size of the substrate. Particles do not move laterally, so they can be printed onto the surface in a pattern which will be preserved as it distributed vertically and then fixed in position through the bonding oven. As well as thermoplastic and thermoset powders for bonding, SAP powders, detergents and flame retardants have been rotary screen applied and used to make a variety of composites and nonwovens. Glass fiber mats and needlefelts of natural fibers have been bonded with up to 60% by weight of PP powder. Spun-laced nonwovens have been impregnated with detergents after drying.

Strahm will not sell the machinery but will sell the process for a licence fee. They have a pilot line which can be rented for prototyping.

Asked if the process would work with carbon powders, Mr Haas said it would, but would fail if carbon fibers were used. Operating speed would depend on the length of the electric field but it could be built to run sufficiently fast to work on an air-lay line. The powder can be shaken out before bonding and the impregnated web must be handled carefully. A mixture of powders may tend to separate in the field. There were no powder losses – nothing went straight through, and the running costs were low because negligible current was needed to create the voltage.

Airlaid v. Spunlace in Wipes

Phil Mango (Consultant) estimated the disposable wipes business to be worth $6billion at retail – 3x the 1997 value. The substrates were mainly air-laid thermal and/or latex bonded pulp/fiber mixtures or carded spunlaced fabrics.

• Globally spunlace was now in the lead with 150,000 tonnes while air laid had 100,000 tonnes of wipes sales.
• Total wipes worldwide amounted to 345,000 tonnes, 70% consumer and 30% industrial. Of the consumer wipes, 58% were Baby Care, 30% Household and 12% Personal Care.
• Air laid capacity (420,000 tonnes) was a little higher than spunlace (400,000 tonnes).
• Demand was about 75% of capacity in both cases, but the announced expansions in spunlace meant that the sort of overcapacity which plagued air-laid a few years ago could now begin to affect the spunlace sector.
• The air laid overexpansion was a blunder with both leading companies assuming they would get 100% of the growth, maybe linked to an over-reaction to the potential for preformed diaper cores.
• 21 of the installed air-laid production lines were M&J system, 22 were Danweb, 5 were Honshu and 2 were J&J.
• 23 of the installed air-lay lines could use both latex and thermal bonding, 15 were latex-only, 10 were thermal-only and 2 used hydroentanglement.
• Buckeye were the largest air-layer with 20% of the world's capacity, Concert (17%) and Georgia Pacific (14%) were 2 nd and 3 rd .
• Dupont and BBA were joint first in spunlacing with 14% of the world's capacity each. PGI had 13%, Orlandi 9%, Jacob Holm 8%, and Ahlstrom 7.7%. (The figure for Suominen – 10,000 tonnes- was well short of reality.)
• In 2006-2007 a further 60,000 tonnes of spunlace is due to come on stream including new lines at Ahlstrom, Orlandi and Spuntech in the USA .
• Air-laid should be the process of choice where the wipe had to be impregnated with solids, where true dispersibility was needed or where heavy basis weights were required.

In response to questions Mr Mango said airlace was a special version of spunlace rather than an air-laid nonwoven. Spunlace was best for super-softness. He thought big Chinese installations of either technology would impact the West either by displacing exports to China or by being exported while domestic demand caught up.

Alternatives to SAP

Fred Barlow (Consultant) offered some theoretical solutions to the SAP availability issue. The industrial revolution had commenced with the switch from wood to coal, had continued in the 20 th Cy with the switch from coal to oil and could be expected to switch back to biomass during this century. So how could biomass aid SAP supply?

• There was a biomass-to-acrylic acid route under development at the Pacific Northwest National Laboratory (funded by the US Department of Energy) which utilized the fermentation of glucose to lactic or 3 hydroxy propanoic acids or aldehydes which could then be converted to AA with acetic acid and calcium sulphate.
• Fluff pulp used to be modified by wet-cross linking or grafting to make a more absorbent pulp which was not sensitive to salt concentrations. A diaper with 100% wet cross linked pulp was said to be equivalent to a 60/40 pulp/SAP mixture for absorbency.
• Monocellulose acetate can cross-link to give a more absorbent pulp (USP 5142034). This is a natural product and might be biosynthesizable given genetic modification of plants.

Asked how soon these could be commercial, Mr Barlow said the bio-acrylic acid was in testing now, and the wet cross linked pulp could be mass produced in about 9 months.

Swiffer Development – NIH OK!

Kent Lynde, Associate Director of P&G Global Household Care R&D described how P&G's unlikely but successful collaboration with their main Asian competitor Unicharm had helped create their latest billion-dollar business – Surface Care. Doubling P&G's business in 10 years means coming up with 500 new ideas each worth $100 million, and this could not be done simply by relying on the internal resources which work so well for incremental projects. So P&G's “Connect and Develop” program is creating a global inventor database and encouraging the use of external sources for big ideas. The target is to source 50% of the new technologies from outside P&G according to CEO A.G. Lafley, but without outsourcing R&D. After the successful launch of Swiffer Dry (1999), Swiffer Wet (2000) and Swiffer Wet Jet (2001) P&G turned to the Unicharm Wave Handy Wiper – the most successful disposable duster in Japan – for their next major surface-care product. Swiffer Dusters, based on an across-the-board collaboration with Unicharm, were launched in 2003 and became an immediate success in the USA gaining an 80% share and exceeding expectations by a factor of two. Global sales are now hundreds of millions of dollars and this new category is spawning new competitors daily. The nonwovens industry benefits from a major new outlet, in this case a thermal-bond laminated with tow fibers for maximum dust pick-up. The partnership with Unicharm allowed P&G to get a superior product to market in less than half the time it would have taken internally.

In response to questions:

• Swiffer Dusters use the same structure in every market.
• The tow is a mixture of polymers.
• They are not biodegradable and will have to be landfilled.
• P&G Japan, normally head-to-head with Unicharm, accept the arrangement. “We have firewalls”.
• The IP is owned by Unicharm. P&G operate under a licensing arrangement.

Faith Healing with Holofiber®

Keith Carnes of Wellman Inc. described fibers containing “naturally occurring optically responsive particles which recycle the energy released by the human body”. These solid fibers, looking remarkably like over-delustred polyester under the microscope, convert body heat into “wavelengths which are accessible to mitochondria, allowing them to increase the level of oxygen at the skin surface”. Wearers of textiles made from the fibre claim relief from pain, jet-lag, exhaustion and also experience enervation and increased physical strength. The garments also made you feel warmer and most importantly, increased transcutaneous oxygen levels (TCPO2).

Clinical trials on diabetics in Veterans Hospitals measured blood oxygen levels in hands and feet after wearing gloves and socks containing the fiber. This was a double-blind trial with ordinary polyester as the control. TCPO2 increased by 8-12% which according to Dr Lavery, the consultant used by Wellman, were compelling and significant and could be expected to increase circulation, reduce pain etc. A second clinical on healthy 18-50 year olds showed an average TCPO2 gain of 25% for the gloves (100% Holofiber) and 10% for the socks (50% Holofiber).

Commercial proving trials are now underway, with the TCPO2 benefits being confirmed in sports socks (13.5% TCPO2 increase), support socks (20% TCPO2 increase) and body pillows (a 9% TCPO2 increase if you snuggle up to it in bed). Thermography is showing that these garments increase body temperature by 6-8F even though they have no effect on heart rate. The development is a joint venture with Hologenix LLC, who was licensing new applications for the particles.

Spunlacing Spunbond

Dr Ullrich Münstermann of Fleissner GmbH estimated 2005 spunlacing capacity at 400,000 tonnes and the production of spunbonds (using INDA data) at 2 million tonnes. However the current production of spunlaced-spunbond was less than 5,000 tonnes. He further broke down the spunlacing market for 2004:

• 220-260,000 tonnes being carded staple
• 50-55,000 tonnes being carded staple with pulp from tissue
• 90-130,000 tonnes being carded staple with air-laid pulp
• 21-26,000 tonnes being wetlaid
• The estimated total spunlace from this slide was 435,000 tonnes

In 2003 spunlaced accounted for only 30% of the North American wipes market (c.f. 66% in Europe), but this was now increasing sharply due to the P&G decision to replace air-laid with spunlace.

Fleissner's Aquajet spunlacing system had evolved sufficiently for them to offer two possibilities involving spunbond: to soften and bulk a thermally bonded spunbond to make it more textile-like (“Water-jet texturizing”), and to fully-bond a spunbond-pulp-spunbond laminate for wipes, both at speeds up to 600 m/min and widths up to 5.4 meters.

For the wipes option, they proposed 48 gsm of air-laid pulp bonded between two 8 gsm polypropylene webs and claimed this would halve the raw material costs (compared with a 70/30 viscose/polyester) to €0.762, assuming viscose at €1.7, polyester at €1.1, PP Chips at €0.8 and pulp at €0.75, all on a per kilo basis. The spunbond – airlaid – spunlace line would produce 35,000 tonnes/year and having lower fixed costs would allow wipes substrate to be made at 65% of the current costs of the viscose/polyester blend on a 12,000 tpy 2-card line. The proposed line would use a single bonding zone working on the three-layers.

Asked how much pulp would be washed through the 8gsm PP bottom layer in the bonding process, Mr Munstermann thought 10-15%, adding this would be easily dealt with in the water recycling system.

Testing Flushables

Ron Jones of Air Products Polymers LP reviewed the methods used to assess the dispersibility of nonwovens, including the P&G/WERF method, and mentioned the soon-to-emerge INDA/EDANA method. APP had looked at the NSF beaker snag test, the tube dispersion test and the orbital shaker method and decided to develop their own method – The Hobar Test. In this test a real toilet was used, but unlike the methods at WERF, NSF or Herriott-Watt University (UK) the, outlet pipe was short and dumped the contents of the flush onto a screen. If the sample has enough integrity to be removed from the screen and reflushed, this is done, up to five times. If it survives 5 flushes and remains handleable it is deemed not flushable. Toilet papers pass the test.

6 flushable commercial wipes were evaluated on these four methods, along with one non-flushable commercial wipe and two experimental samples made by APP. The APP Hobar test passed the two samples made by APP and failed the rest. Snag break-up only passed one of the APP samples while the shake-flask test and the tube-dispersion test both passed both APP's and a 48 gsm commercial HE rayon/pulp 7”x10” household wipe. The bonding methods used were not revealed other than the best of the APP samples being PVOH/boric acid the other “using sodium sulphate to develop lotionized wet strength”. APP argued that these binder systems would be fine for kitchen/bathroom applications if not for personal care.

Asked about the salt concentrations used in their experimental samples, Mr Jones said 4.5% boric acid in one and 7.5% sodium sulphate in the other.

The Future of Flushables

Richard Annis of Ahlstrom Fiber Composites Division pointed out that the flushing of wipes was having an adverse effect on municipal wastewater treatment, attracting negative press in both Europe and the USA and legislation was now emerging to ban their disposal in toilets. This could even rule out wipes designed to be flushable.

Criteria for flushablility, according to EDANA/INDA will be:

1. Does not block the pipe work.
2. Has no effect on either municipal or septic tank treatment systems.
3. Has no effect on the environment – visibly or chemically.

Products which are flushable by size only will meet 1. but may cause problems with 2. and 3. The target is toilet-paper levels of flushability with wet-wipe levels of wet strength, and this is not achievable using conventional bonding systems. Water soluble binders have to be used and these must be strengthened by the lotion and weakened when diluted with the flush water. Examples are PVOH binders with borates in the lotion, Polyacrylic/methacrylic binders with calcium in the lotion and newer polymers (unspecified) with high sodium concentrations in the lotion. Of these the PVOH's and polyacrylics have not found wide acceptance due to their potential to irritate sensitive skin, and/or their failure in hard water areas, and/or the added complexity of lotion formulation. The newer sodium-triggered binders are still under development but look better.

Ahlstrom's Dispersible Hydraspun is a hydroentangled wet-laid blend of pulp and short viscose or lyocell. Unlike fibers of cardable length these disentangle relatively easily when wet and provide a firmer foundation for flushability claims. In the Tube Dispersion Test, Hydraspun 784 breaks up in 18 turns while an air-laid “flushable by size” moist toilet tissue is still intact after 50 turns. Independent testing at Courtray Consulting, Brunel University and the Stevens Institute confirm both the dispersibility and the biodegradability of the material,

Bicos based on Polyester for Airlaid

Jörg Dahringer of Trevira GmbH, Germany reminded us of the advantages of a PET/PE bico fibre over the more commonly used PP/PE:

• At the same decitex, the PET product has a lower diameter and hence higher bonding efficiency.
• The melting point differential between PET and PE is 120C yielding a less critical bonding process.
• The PET core is stronger than the PP core.

Trials with variations on Trevira Type 255 - a 1.7 dtex/6mm 50/50 PET/PE bico - in blends with woodpulp yielded the following conclusions:

• The optimum decitex (for highest nonwoven strength) was 1.7
• Strengths increased as staple length increased from 3-12mm, with a hint of a plateau between 6 and 9mm.
• Removal of the coupling agent from 1.7/6mm T255 reduces the nonwoven strength from 33 to 8 N/5cm. (The coupling agent is added to the PE sheath to improve bonding to cellulose.)
• The optimum core-sheath ratio was 50/50. (60/40 and 35/65 giving significantly weaker nonwovens)
• If the core was off-center in the sheath, the fiber and nonwoven could be further bulked by heating to 120C. This allowed latent spiral crimp to modify the mechanical saw-tooth crimp added for processability.

The Future of Air-Laid ?

James Westphal of Troika Technologies Inc reviewed the history of air-laying from the original Kroyer process to the recently announced Celli former. Because all of these systems use a screen through which the fibers have to pass, their productivity and long-fibre handling capabilities are limited. He suggested the way forward was exemplified by the screenless former invented by Carsten Andersen of Formfiber Denmark and described in US 2005/0098910. This system is said to be capable of:

• 700kgs/hour/metre per forming head,
• Handling dust up to 50mm staple fibers
• Operating with “Zero Waste”
• Manufacturing 50 – 5000 gsm webs.

The equipment is intended for making heavyweight waddings and insulation panels out of coarse fibers such as hemp, flax and reclaimed wool and as such will be appropriate for a heavier range of products than today's other air-laying processes. Nevertheless, directionally, screenless systems appear to offer development potential for lighter, longer-fibered products.

Hook and Loop Fasteners

Rob Cesena of 3M promoted their range of fasteners. Of interest to the hygiene products producers were:

• The extrusion bonded nonwoven loop (“EBL”) which looked like a parallel-laid web, gear crimped into waves and locked into this state by extruding a polymer film onto the back. Said to be low price with premium look and feel.
• Knitted loops, looking like air or water - jet texturized lightweight knits (plain or velour) made of continuous filament yarns and bonded to a printed film backing.
• Micro-replicated hooks formed by film extrusion onto a mold which creates vertical “posts” on one surface. The tips of these posts are melted to create a mushroom shape which can attached to looped fibres.
• Profile-extruded hooks appear to cast film onto a mold which forms continuous ridges with a mushroom-shaped section. These ridges are then cross-cut prior to MD stretching the film to create the individual hooks.

Asked if they had any hook systems which would work with plain spunbond, Mr Cesena said they did not. For adult hygiene products the principles were the same as for baby products only the hooks and loops had to made bigger.

Submicron Meltblown

Detlef Frey, the R&D Manager of Reicofil, said Reifenhäuser has split into two and Reicofil is the new name for the nonwoven division, the other being packaging. Their recent work to optimise the melt-blowing process involves:

• Allowing adjustment of the inclination of the forming conveyor to optimize the pore structure and laydown of the web.
• Recognizing that losses of barrier properties (hydrohead) are due mainly to small holes in the web, these being mainly associated with “shot” (blobs of polymer formed when a filament breaks close to the jet).
• Working to minimize shot by optimizing the machine set up, thereby increasing hydrohead from 600 to 800 mms water. Part of the change involves moving from 25 to 35 holes per inch without increasing throughput.
• Optimizing the resin properties to minimize shot thereby increasing the hydrohead from 800 to 1000 mms water.

The “new technology” arising from this optimization allows the production of finer fibers than hitherto possible. 40 gsm webs now allow filtration of 95% of 0.392 micron particles at a pressure drop of 250 Pa according to DIN EN 1822-1.

Asked what percentage of fibers in this improved web would be below a micron, Dr Frey admitted that they could not measure this. They preferred to look at bulk properties such as hydrohead. What resin variables other than MFI could be changed? They had focused on reducing the coefficient of variation of MFI.

Atmospheric Plasma Update

Rory Wolf, VP Business Development for Enercon Industries described how they had combined their plasma treatment (APT) with photografting to achieve permanent improvements in the wettability of polypropylene. The roll-to-roll process now works at commercial speeds and the dielectric barrier discharge “glow” is relatively cool at 300C: the plasma power density being insufficient to damage a nonwoven.

An 18gsm spunbond was passed through the APT station running at 2.2 kW output power and using 6.4 l/min of helium and 1.6 l/min oxygen. 1 gsm of water based photoinitiator was printed on, IR-dried and UV-cured. Surface tension increased from 34 to 54 dynes/cm through APT and stayed at this level through photografting. Neither the odor nor the color of the spunbond are affected by the treatment. The main objective appears to be to improve the printability of the nonwoven, and much enhanced peel adhesion was claimed (7 fold increase on APT alone and 8-fold after APT + photografting.)

In response to questions:

• Visual graphics quality is much improved by the treatment.
• Water-based flexo-inks can be used
• Energy consumption in APT is 1/3 rd that of corona treatment.
• Gas losses on the 16” line cost $2-3 per hour.
• Process speed? not revealed but the line is designed for 1400 ft/min.
• There are no health/safety issues. Ozone levels in the gas remain below 15 ppm.
• The maximum surface tension achieved on PP is 72 dynes/cm – before photografting but presumably not permanent.

New Polyolefin Fibers?

John Wolhar of FiberVisions Inc. first addressed the supply problems. World polypropylene capacity is increasing and some of that capacity will use new propylene technology which is less dependent on oil. Prices will return to normal, polyester will always be more expensive than PP, and rayon will continue to be volatile but overall, despite its lesser dependence on oil, would maintain its price relationship to cotton and the main synthetics.

FiberVisions “Hy-Wettable PP” can be hydroentangled into a durably hydrophilic nonwoven with about 80% of the total capacity of a rayon nonwoven in a detergent-free test. In wet-wipe storage testing the top layer wipe of a 70/30 HWPP/PET stack is wetter than the control 70/30 rayon/PET stack after 3 weeks, but the bottom layer wipe is, if anything, slightly wetter also. The wipes are stronger and bulkier when the rayon is replaced by HWPP.

Major increases in bulk can be obtained by layering a new “Hy-Shrink PP” with regular webs prior to thermal bonding. The thickness of the nonwoven doubles from 1mm to 2mm in through-air bonding.

Also mentioned:

• Finer fibers are available for increased strength, softness and cover.
• Thermal bonded blends of regular or Hy-Shrink PP with HY- Wettable PP would allow the production of low-cost wipes with high bulk, softness and recyclability.
• Fine denier polyethylene fibers are now commercial and give outstanding softness.
• Polyolefin binder fibers can be used to bond natural fibers into strong, lightweight structural composites.

In response to questions, the Hy-Wettable PP does not imbibe water, it just has a durable surfactant at the surface. This additive adds 3-5% to the fiber cost. Were there any new ways to improve the efficiency of bonding bico fiber to pulp in air-laid? None that Mr Wolhar was aware of.

A Pill for Incontinence?

Pricie Hanna, VP of John Starr Inc, previewed a study done with Helena Engqvist Consulting on the likely impact of advances in drugs on the market for hygiene products. The prevalence of incontinence is rising due to population ageing and the increasing prevalence of prostate surgery, obesity and diabetes. By 2050, 20% of the world's population will be over 60, including 35% of Europe and 26% of the USA . The key pharmaceutical companies developing drugs to treat incontinence include Pfizer, J&J, GlaxoSmithKline, Ely Lilly, Novartis, Yamanouchi and P&G. Several new drugs for over-active bladder were introduced in 2004 and 2005 and many more are in the pipeline. Stress incontinence is proving harder to treat, with one new drug using dulozetine approved in Europe but not in the USA . Also in 2005, collaborations between P&G and Novartis, Yamanouchi and GlaxoSmithKline and Takeda and Toray were announced, all targeting faster introductions of both prescription and OTC products to treat incontinence. The bottom line? Drugs will reduce the market for absorbent products but the impact will not be felt for about 5 years when OTC sales will commence. Ms Hanna was unaware of any documentation on the size of the obesity effect, and with regard to the impact of drugs on the feminine hygiene market, that would be the subject of another study.

Competitive Intelligence

Gerri Potash of Nerac Inc suggested using the following sources to obtain information about competitors:

• Web-logs or Blogs: contain much useful comment on product performance but with 18.5 million in existence even keyword searches fail. Here Intelliseeks Blogpulse can help.
• Competitors web-sites can be monitored automatically for changes.
• Contacting their customer service department to obtain newsletters and literature adds perspective.
• Corporate authors' contributions to peer-reviewed technical literature and trade journals could be monitored.
• Patent and trademark databases can provide early indications of new product development.
• Market studies and reports are often abstracted for trade magazines. Sometimes they can be purchased in sections to reduce cost.

Skin Care Issues

Beth Hanson of Marketing Technology Services reviewed the anatomy of diaper dermatitis and ways of preventing it. While it's incidence has fallen dramatically as disposable diapers became drier, she felt further improvements are still possible:

• More air is needed in diapers – they should be made more breathable.
• Barrier protection for the skin could be incorporated in baby wipes or coverstocks.
• Baby wipes should use lower pH lotions.
• Users of diapers should be provided with more dermatitis-prevention information on packs and websites.

Bicomponent Spunbond and Meltblown

Mark Snider of Nordson Corporation provided a basic introduction to bicomponency leading to a description of the features and benefits of their NanoPhase bicomponent meltblown technology. This bico system allows normal throughputs to be used while obtaining submicron fibres from segment-pie extrusion. Asked how the segments were separated after formation, Mr Snider said they fell apart in the turbulent air, the polymers and additives having been chosen to prevent the segments from adhering together. The meltblown webs can be calendered to give microporous films.

Biodegradable Nonwovens

Frederic Noelle of Rieter Perfojet described trials with wipes substrates where PLA had replaced the polyester. Old data from Courtaulds (circa 1990) showed how lyocell, viscose and cotton degraded in a sewage farm and old data from Cargill-Dow showed how PLA degraded after pre-hydrolysis. Then wipes disappeared in 60 days. Asked if there were any issues processing PLA, shrinkage was mentioned.

Hard Surface Cleaners

Jim Hanson of MTS Inc is testing a wide range of hard surface cleaning products and will soon be offering a report for sale. This paper provided a glimpse of the methodology and results. The best was “Swiffer” (dry) and “Mr Clean” (wet).

Value Added Printing

Jim Robinson of PCMC re-read the paper given at INTC – St Louis by co-author Kevin Marrick. In response to questions he said the big growth area now under development was the printing of diaper topsheet. They were collaborating with a speciality ink producer. Expandable inks used 3-4 micron particles in suspension. Printing on spunbond could be done reliably providing the basis weight was not too low.

Hydrogen Bonded Air-Laid?

Bob Makolin (Consultant) marvelled at the way hydrogen bonding increased the strength of a paper as it dried and wondered if the method could be used to increase the strength of air-laid nonwovens. He concluded that the high levels of moisture, heat and pressure needed to form hydrogen bonds are not usually present in air-laid processes and capital availability will dictate the speed with which the technology becomes fully developed.

Miscellaneous

Technical Absorbents Ltd (UK) have several interested buyers, one being prepared to put in the necessary expansion and longer-range strategy. The superabsorbent fiber plant has been stretched to 3200 tonnes/year and is still oversold, mainly into food packing soaker pads. Expansion to 10,000 tonnes/year would be possible on-site with the right investment. The neighboring acrylic fibre plant is closing and a buyer is interested in the tow production (carbon fiber precursor).

Natureworks LLC is making progress with cost reduction and can now match polyester chip prices with the lower melting point PLA. They seem to be disenchanted with textiles having learned the hard way that fibers with melting points like PP are not good in durable garments.

Tencel ( Mobile ) is still at half rate following Katrina.

BBA's Materials Division – the nonwoven production division - is likely to be demerged or sold off to allow more focus on their main aerospace business. Their Chinese air-lay operation is already up for sale.

Link to Photograp

INTC, St.Louis, Sept 19th – 22nd 2005

Key Points

• Polypropylene, polyester and cotton prices correlate well with oil-price over long periods of time.
• Hollow nanofibers have been obtained by sheath-core electrospinning of polymer on oil. Titania loaded versions have been calcined into tubular anatase fibers and aligned into bundles.
• Cellulose acetate has been electrospun from acetone/water solution and deacetylated to make pure cellulose microfibers.
• Nanofibers of polyethylene-oxide loaded with titania or magnesium oxide nano-particles have been electrospun. Chitosan/silver nanofibers are being developed.
• Nano-clay dispersions in aqueous polymers allow submicron coating to achieve barrier properties without affecting texture.
• Printing with functional “inks” can add local absorbency, odor control, differential drainage, hydrophilicity or hydrophobicity to a nonwoven.
• Freudenberg is commercializing Novolon®; deeply embossed microfiber fabrics made possible by spun-laying and entangling unoriented bico fibers.
• Hills Inc is testing an 8000 holes/m meltblowing dye for high productivity.
• Elastic spunbonds are now being sold by BBA in Germany , but not for diaper components.

The main INDA-TAPPI conference was preceded by a 1 day Nonwoven Enhancements conference organized in conjunction with the American Association of Textile Chemists and Colorists. Both Conferences are reported below, but the main INTC conference comprised 3 simultaneous sessions and only those attended are reported. The full set of papers will appear on www.inda.org/papers/intc2005 for a limited period and can be accessed by means of a password provided to attendees.

This was the largest and busiest nonwoven conference of recent years comprising 98 full presentations, 14 Poster presentations, 12 Supplier showcase presentations, 18 award presentations and a fashion show.

Oil/Fiber Price Relationships

In this keynote speech, Ian Julian of Chemical Market Associates Inc., explored how oil price fluctuations occurred and how they affected the prices of polyester, polypropylene and cotton. Crude oil price is driven by supply and the demand from the transport (95%) and petrochemicals (5%) industries, and by emotion. The USA supplies 10% of world demand but uses 25%. OPEC supplies 40% but consumes 10%. Saudi Arabia produces more than half the OPEC total and is the flexible producer who normally adjusts output to meet total demand. However since 2004 production has run very close to capacity with little spare. Contracts for oil on the futures market run at 10 times the level of the physically available oil. China 's demand is up from 6.3% of global supply (2001) to 8% in 2005 driven not only by vehicle use, but also by the more prosperous population installing air-conditioners. Currently the Chinese electricity supply industry is using diesel-powered generators to cover demand surges in the summer months. Overall, oil is in short supply and prices will stay high for some time.

Natural gas follows crude oil pricing and 95% (methane) goes into fuel while 5% (ethane and propane) goes into petrochemicals. All the USA 's easily accessible natural gas has gone and imports of liquefied natural gas are needed. Shipments of LNG are currently limited by environmental issues associated with cooling and warming-up the gas.

Polypropylene chip price is now 81% raw materials (67% in 2001) and the correlation with oil price is good. From the graphs presented, fiber grade PP chip price in cents/lb is ~15% more than the WTI oil price ($/barrel) was two or three months previously, spikes in oil price excepted.

Polyester shows a similar correlation, the polycondensation chip price being ~35% above the WTI oil price in $/barrel. However in June 2005 polyester came down to 62c/lb while oil continued to rise to 60 $/b, but according to Mr Julian, polyester prices will get back into step if the crude oil price stays high.

Cotton too has tracked oil closely, the cotton A index (c/lb) historically being roughly double the WTI oil price ($/b). Cotton yield reflects the amount of petrochemical-based fertiliser and pesticide use, and the harvesting/transportation oil consumption is significant. Cotton is also tied to polyester price. However the good correlation broke in May 2004 when an unexpectedly high cotton crop revealed itself, cotton declining from ~70 c/lb to ~60c/lb while oil price doubled. This “hiccup” will be corrected over the next 12 months as the supply/demand balance corrects itself.

Spunlaced Spunbond

Alfred Watzl of Fleissner GmbH said the world capacity for producing spun laced fabrics was 435,000 tonnes in 2004 , this being broken down by laying process as follows:

All staple fiber – 220-260,000 tonnes

Staple/tissue composites – 50-55,000 tonnes

Staple/air-laid pulp – 90-130,000 tonnes

Wetlaid – 21-26,000 tonnes

Spunlaid - <5,000 tonnes

The most important end-use was wipes, and here Dr Watzl foresaw growth in the pulp-containing variety, especially the SPS trilaminate using two thin skins of PP spunbond to contain the air-laid pulp, or if one absorbent surface was needed, an SPC trilaminate (card web hydroentangled onto one face.) For the SPS product the raw material cost savings compared with the current polyester/viscose staple wipe substrate would be 50%. (€1.52/kg for the 70%CV/30%PET down to €0.76/kg for a 25%PP/75% pulp trilaminate product). Total cost comparisons suggested a 35,000 tonne spunbond/airlaid line would produce substrate at 65% of the cost of a current 12,000 tonne 2-card line using CV/PET staple. There was the additional low-cost option of buying commercially available diaper topsheet spunbond and laminating it either side of a commercial tissue on an Unwind/HE bonder/dryer/winder combination.

For durables, the hydroentanglement of polyester spunbond for roofing applications was now feasible, and HE was shown to give double the MD and CD strengths of needling. The additional cost of energy to achieve this is negligible now that bonding was possible at 200 m/min.

Elastic Bicomponent Spunbonds

Jared Austin of BBA Fiberweb reviewed the advances in spunbond technology from the first attempts to adapt multi-jet continuous filament yarn production using draw-guns to stretch and lay the fibers through the Lurgi, Dupont, and K-C systems to the advanced draw-nozzle/vacuum Reifenhauser bico process. The BBA/Dow Chemical JV – Advanced Design Concepts – has now produced “Dreamex” elastic bicomponent spunbonds on a heavily-modified Reifenhauser line at a commercial scale at BBA's Linotec subsidiary in Germany . 13,000 filaments of thermoplastic elastomer (95%) are coated with a thin sheath of polyethylene (5%), laid, incrementally stretched in both the machine and cross directions, and finally heat set by through-air bonding. The stretching process drops the fabric basis weight by 50% and the fiber deniers by 30% - a valuable increase in area-yield for a disposable fabric.

If the fibers are “tipped trilobal” bicomponents with PP tips on a PU trilobal, the stretching process splits off the tips to give three sub-denier microfibers of PP for every triobal elastomer. The resulting fabric has an interesting suede-like texture.

For the future Dr Austin saw

• the commercialization of versions using the more economical elastic polypropylene
• the production of durable dyeable fabrics with polyester or nylon sheaths
• the evaluation of styrenic elastomers
• spunlaced elastomeric spunbonds (done off-line initially because BBA does not have HE and spunbond on the same line.)

Diaper side-panels will not be made using this technology until the quality of elastic PP polymers improves.

Melt-blowing Elastomers

Dr Stephen Michielsen of NC State has investigated the structure and properties of a series of melt-blown polyether-based thermoplastic polyurethanes . Three hardness grades with hard segment chemistry based on 4,4-diphenylmethane diisocyanate and 1,4-butanediol were used. Because none of the polymers were available with rheology suitable for melt-blowing they had to be extruded at temperatures of 244, 267 and 280C (respectively for each hardness level) and these temperatures caused degradation such that the fabric molecular weight was half the chip MWt. The fabrics were produced at 14, 20 and 30 cms Die-Collector Distances and at two basis weights.

Mean Fiber diameters were typically around 5 microns (0-20micron range) i.e. similar to polypropylene. Using the “dogbone” tensile method (preferred for samples which otherwise break at the clamps of the Instron), best results were obtained at the short DCD and with the harder polymers. Increasing DCD gives weaker and less extensible fabrics suggesting that the inter-filament bond strength is insufficient at the higher DCD's. This in turn could be due to the extra time allowing the polymer to crystallize more completely. Did the orientation of fibers in the web change with DCD? Dr Michielsen said it did not.

PET Spunbonds for Durable Nonwovens

Dr Alberto Lorioli of Meccaniche Moderne SpA ( Italy ) described the development of spun-laid needlepunched PET for applications requiring anisotropic, uniform fabrics of high tensile and tear strength and high thermal stability. Key variables affecting the fabric properties were:

• PET polymer rheology, Molecular Weight Distribution, and oligomer content
• Controlled moisture and crystallinity on entering the extruder
• Extruder screw profile, and the resulting melt temperature profile
• Polymer filtration prior to spinning
• Spinneret hole diameter, L/D, number of holes and the hole pattern
• Quenching/fume removal
• Stretching ejector details (geometry, no of fils, air pressure, temperature)
• Draw ratio

Unlike typical PP spunbond, the MM SpA PET system uses small round spinnerets fed from individual spin pumps, the “yarn” from each jet being stretched in its own oscillating air-gun prior to laydown.

A correctly set up process could produce PET filaments of 32 cN/tex tenacity with extensions less than 100%, whereas “narrow distribution” PP filaments used for coverstock had 20 cN/tex tenacity and 350% extension. Metallocene PP gave 31 cN/tex and 200% extension. Fiber laydown pattern is determined by the setting of the “flappers” which oscillate the ejectors to control filament direction and distribution at the conveyor. High stability fabrics require “real” (as opposed to flat calendar) heat setting where the web is held to width in hot air on a tenter frame.

Electrospinning Biodegradables

Chunhui Xiang of Cornell University has electrospun both cellulose acetate and PLA and used dye uptake and release as a measure of their potential to deliver chemicals. A 17% solution of acetate in an acetone-water (17/3) mixture was electrospun and then deacetylated with 0.05M NaOH in ethanol to give what FTIR proved to be a 100% regenerated cellulose microfiber. PLA was electrospun from an 8% solution of the polymer in a chloroform/acetone mixture. Direct dye uptake by the cellulosic was about 3 times that of cotton. She concluded that high surface areas allow higher levels of chemical uptake and release. (Student presentation – paper not available)

Hollow and other novel nanofibers

Jesse McCann of the University of Washington ( Seattle ) has co-spun sol-gel precursors with an ethanol soluble polymer , and has extended this system to spin composite fibers with excellent size control down to tens of nanometers. Using a coaxial spinneret, he has been able to manufacture porous, hollow and core-sheath nanofibers and control the surface chemistry of those resultant fibers by tuning the core and sheath solutions. Patterned collectors have allowed the parallel alignment of arrays of nanofibers. These arrays could be readily be crosslaid into intriguing woven-like structures.

Metal-alkoxide precursors in polyvinylpyrrolidone were dissolved in ethanol or isopropropanol and spun, and when the PVP was dissolved porous nanofibers of the conjugated polymer remained. Burning off the organic matter yielded metal-oxide fibers (Tin or Titanium). Calcination of fibers made with amorphous titania for 3 hours at 500C yielded polycrystalline anatase fibers . Perfect hollow tubes of these oxides were obtained if the coaxial spinneret extruded viscous mineral oil down the centre. The oil can be a carrier for other materials, iron oxide being an example. Fibers with a titania/PVP sheath had also been made on a polystyrene core. Barium titanate nanofibers had piezoelectric properties.

If the collector had an insulating gap between two plates, the fibers bridged the gap forming a parallel alignment. If the insulating gap was created as a square between 4 electrodes, and opposite pairs of these electrodes were switched on and off alternately, a woven-looking mesh can be obtained. Dr McCann concluded that patterned collectors would enable the assembly of nanofibers into a variety of patterns.

Composite Nanofibers

Dr Sheshadri Ramkumar of Texas Tech. University ( Lubbock ) has shown how electrospun polyurethane nanofibers form in a unique honeycomb pattern on the collector and postulated applications in drug-delivery, protective clothing and tissue scaffolds. He has also added titania and magnesium oxide nanoparticles to a polyethylene oxide solution and spun composite nanofibers with distinct nodes of oxide which more than double the fiber diameter every micron or so. Here a 400,000 MWt PEO was dissolved in water at 4% and extruded at 50 microlitres per minute through a 16 kv field at 20C and 40%RH. When loaded with an unspecified amount of magnesium or titanium oxides, improved toluene absorbtion and UV protection factors were observed. An unspecified weight of nanocomposites were tested on an unspecified active carbon fabric, which also provided the control. Toluene absorbtion increased from 31% to 33%(sic) when the MgO composite was used and to 37% when the TiO 2 composite was used. The TiO 2 composite increased the UV protection factor from 15 to around 500. More detailed testing was promised, and Dr Ramkumar was now looking at Chitosan nanofibers loaded with silver for wound healing.

Nanocomposite Barriers

Harris Goldberg of InMat Inc described their barrier coatings which use nano-sized clay platelets dispersed in an aqueous polymer dispersion. These platelets allow very thin coats to have very high impermeability, and thus allow the development of barrier properties without substantially affecting the other physical properties of the substrate. The technology was developed by Hoechst and used in 1996 by Michelin to coat the inside of tires to reduce air loss while using less butyl rubber to make lighter tyres. In 1999 Dupont bought the technology from Hoechst and InMat is a buyout from Dupont. InMat is developing it for NBC suits which use neoprene and nitrile rubber rather than butyl rubber. They see a big market in packaging due to its ability to reduce oxygen pass through of polyester films to hitherto unachievable levels.

Coating nonwovens with the barrier is impractical because it would be too expensive to fill the large pores. The substrate has to be very smooth and pin-hole free. Nevertheless a 30 micron coat of the barrier is equivalent to 1mm of butyl rubber and can be stretched by up to 30% without rupture, this being enough for most practical applications. Data presented showed that coated PP film performed as well as PET film coated with the same weight. Acrylic films, normally even more porous, were similarly sealed, giving a 150,000-fold reduction in oxygen permeability, compared with the 1000-fold reduction achieved with the same weight on PET.

The main market is currently a coat on the inside of Wilson 's top of the range tennis balls.

In response to questions:

• The coating process currently works at 200 ft/min and applies a 0.2 to 0.5 micron layer.
• Multiple layers are needed if thicker coats are required.
• Normally the nano-coat is protected by a further coat of PE.
• Some customers find the adhesion to this protective PE coat is too low and this needs further funding to solve.
• The coat makes a normally clear PET film very slightly hazy.
• Cost: only pennies per tennis ball!

Submicron Melt Blown webs

Mr H Geus of Reifenhauser GmbH pointed out that making a submicron web out of PP resin involved converting a quarter of a gram of polymer into a filament 1400 kilometers long. Reifenhauser's new meltblown technology gives many more filaments of this size and therefore allows the production of more retentive filters and higher – hydrohead barrier fabrics. Unfortunately patent issues prevented him from telling us how this was achieved. However the emphasis seemed to be on achieving high air speeds (> Mach 1) and filament speeds in the resulting turbulence of 6-10 times the air speed for much of the die-to-collector distance (DCD). Air temperatures were above the melting point of the polymer, and the extra draw-down was achieved close to the exit from the air-knives. Using a higher quality resin was also mentioned.

Bico Meltspun Technology

Dr Hassan Badaghi of Nordson Corp. listed the types of bicomponent fiber and their advantages. In addition to the bonding reasons for using sheath core bicos he added the ability to use virgin sheath polymers over recycled polymer to reduce costs, or to use expensive “functional” sheaths over cheaper cores to make high value products. Side-by-side bicos could, after hydroentanglement be heat treated to create permanent crimp and extra bulk in the final product.

Bico meltblown webs can be split to yield a high percentage of ~1 micron fibers, allowing an SMS structure to have the same hydrohead as an SMMS structure. Direct extrusion of finer fibers is now possible through engineering which allows melt-blown heads to operate either with double the polymer throughput or, to make “NanoPhase” products by reducing the throughput to get finer fibers. True nanofibers can be obtained by splitting melt-blown segment-pie fibers.

Asked what throughputs were possible when melt blowing to get an average fiber diameter below a micron, Dr Badaghi said the die in question used 50 holes/inch and passed 0.17 gms of polymer per minute per hole. The segmented bico MB's were split by using higher pressure air at the die. Did the Nordson process infringe the K-C patent in this area? No, but Nordson were concerned about another companies patents!

Finer Melt Blown Fibers
Arnold Wilkie of Hills Inc mentioned the non-traditional (i.e. not using the original Exxon system) melt-blowing systems before promoting the latest Hills technology :

• Biax-Fiberfilm uses a sheath of hot air around each die orifice.
• Nanoval uses a Laval nozzle to explode the filaments after extrusion thereby achieving higher throughput and finer, fully oriented microfibers.
• Nonwoven Technologies uses a pair of engraved plates to form the die holes and achieves good back pressures from the very high hole-lengths possible.
• Nordson Nanophase (no details)
• NanoTechnics (no details)
• Rieter EMBLO technology. (no details)

Instead of the almost universal “coathanger” polymer distribution, the latest Hills technology uses a multi-pump system to deliver the polymer to segments of the die thereby achieving higher uniformity of polymer flow and temperature while allowing the use of a wider range of rheologies. The die can be either electrically heated or, preferably vapor heated to get exact temperature control. The Hills spinnerets are not drilled but formed from 6 photochemically etched plates, fusion bonded to prevent leakage. This system allows the full range of Bicomponent fibers to be made, thereby allowing true nanofiber production at economical production rates. 4000 holes/metre has been commercialized and 8000 holes/metre is being tested. The plate system allows holes of 0.1mm diameter and 50:1 L/D – this being impossible with drilling methods. Together these innovations allow very low polymer flow per hole yielding finer fibers.

5 of the new lines are now on order – all for Asia . For the future Mr Wilkie mentioned the use of elastic polymers.

Spunbond strength optimization

Dr John Hagewood of NCRC has made a 6 ounce spunbond which meets the grab strength and tongue tear specifications for a 20 ounce woven canvas . Nylon islands in a polyethylene sea were spunlaid at 0, 25, 50 and 75% PE, and 0,1,18, and 108 islands. Of these the 100% nylon and the 75% nylon in 108 islands were judged worth taking into a detailed bonding study using combinations of needling, hydroentangling, calendering and through-air bonding. Thermal bonding after mechanical bonding brought out the best results with calendering at 145C being equivalent to through-air bonding at 160C. Hydroentanglement (two passes) was the best form of mechanical bonding. The bico fabrics outperformed the 100% nylon and the polyethylene content appeared to be crucial to getting the best strengths after thermal bonding. Thermal bonding proved more important than hydroentangling. Attempts to use other bico structures (TPU/PP, PET/CoPET, Nylon/CoPET, TPU/NYLON, and PET/PE gave inferior results, the PET/PE being the best of these and worth further optimization.

Segmented Pie Fibers in Nonwovens

Dr Benham Pourdeyhimi of the Nonwovens Co-operative Research Center has studied the effect of segment number on the properties of nonwovens made from these bicomponent fibers after they had been split in hydroentanglement. The microfibers could also be released by chemical, thermal or other mechanical means, but hydroentanglement had been of most interest to the industry recently. Freudenberg's Evolon® fabrics for instance used spun-laid segment-pie fibers and bonded the webs with high pressure HE, attempting to split and bond the fibers in one step. (Here entanglement restricts the opening up of the fibril bundles so some post-processing of the fabrics e.g. jet-dyeing is needed to achieve the desired softness.)

In this study fibers with 8, 16, 32 and 64 segments were spun from both 50/50 and 75/25 PET/Nylon into fibers with a diameter of 80 microns and nonwovens with a basis weight of 175 gsm and a thickness of 0.8mm. The segment sizes were equivalent to diameters of 4.5, 2.5, 2, and 1 microns respectively. The results of nonwoven testing showed smaller effects than expected, SEM's clearly indicating that the first fibrils liberated were twisted around the main fiber bundle preventing further opening. In the case of the 64 segment fiber, there was clearly a “cuticle” around the circumference of the bundle which also hindered splitting. Washing the fabrics did not improve matters and clearly some very vigorous treatment would be needed to achieve the properties expected from the segment sizes. Overall conclusion? You can't split segment-pie fibers properly using hydroentanglement alone, but the 16 segment products gave the best looking fabrics. Asked if the fibers could be split by needling, Dr Pourdeyhimi said they could not, but needling prior to hydroentanglement appeared to be beneficial to greater fibril liberation, maybe by damaging the fibers and maybe by creating spaces into which the fibrils could move. Short fibers ought to be easier to split (Wet-laid HE) but this had yet to be tried.

Modifying Polypropylene Nonwovens

Dr Sandra Schmitt reviewed the methods available to alter the surface properties of a PP Spunbond:

• Modify the polymer chain
• Melt additives
• Coating or finishing the nonwoven
• Grafting new chemistries onto the surface.

Chain modification can be achieved by the addition of suitable co-monomers (but the examples given did not apply to PP). Maleic anhydride can be chemically linked to PP to make masterbatches showing carboxyl functionality. Acrylic acid and other reactive molecules can be grafted onto the surface of PP after its activation by plasma treatment, but the resulting hydrophilicity tends to diminish with time. Surface finishing or coating can also give transient hydrophilicity. Overall, the durable effects were obtained with chemistries unlikely to appeal to the hygiene products producers.

Biocidal Halamines for Nonwovens

Dr Gang Sun of UCAL (Davis) made the case for antimicrobial textiles and polymers. One in twenty in-patients attending US hospitals develop infections and 88,000 of these 1.8 million nosocomial infections prove fatal. 97% of the infections are caused by “medical materials surfaces” such as nurses uniforms, stretchers, beds, tables chairs etc. SARS in particular survives longer on surfaces than other microbes, and has been seen to infect staff wearing full protective kit. Staph.aureus and MRSA infections doubled between 1987 and 1997 and the % of MRSA also doubled to account for 50% of the total.

A successful antimicrobial must be fast acting, broad spectrum, non-selective, unable to encourage the development of resistant organisms and non-toxic to higher life forms. Simple inorganic biocides such as hypochlorites, and peroxides are contenders, but halamines were, in Dr Sun's, view the best possibility for fabrics because they released chlorine slowly and could be regenerated by bleaching with hypochlorite. Halamines could be created from the usual permanent-press finishing chemicals such as DHDMEU and these could be grafted or cross-linked onto cellulose. Data showed the treated textiles as effective against a wide range of organisms and while the efficacy deteriorated on washing, it could be regenerated if hypochlorite was used in the washing process. Another compound (ADMH – the acronym not being explained) could be grafted onto any polymer and allow halamine functionality to be created on the surface.

Dr Sun is now exploring adding halamines to extruders making spunbonds. Asked if the halamines had been registered as pesticides he commented that it is the chlorine not the halamine which is the active ingredient and this is registered (so the halamine is not?) Did the effect work at high humidities? Yes, socks using halamines had been continuously worn by troops for 5-days without any fungal infections – or any other problems – developing.

Vis-Breaking Additive for Melt-Blown

Matthew Gande of CIBA Speciality Chemicals described their new additive “FRG-1”, a hydroxylamine based polymer degrader which can be added to the extruder to increase the melt-flow rate of polypropylene. Although their old additive “Irgatec CR 76” was not mentioned, FRG-1 appeared to be the same material, several of the graphs being the same as those used by CIBA's Paul Shields for his paper on Irgatec CR 76 at Insight 2004. Mr Gande however presented more detail.

The effects of the additive on a 35 MFI PP could be varied by altering its concentration, the extrusion temperature or the dwell time (throughput). Fiber diameter reductions appeared most sensitive to the peak temperature used in extrusion. Using 2% FRG-1 below 270C had no effect but at 275C the mean diameter had fallen to 2 microns (from 3), and by 285C the mean diameter was down to 1 micron. Reducing the throughput from 1 to 0.4 gms/hole/min reduced the mean diameter from 3 to 2microns (2% additive at 275C). At 0.6 gms/hole/min and 275C, increasing the additive concentration from 0 to 3% also reduced the mean diameter from 3 to 2 microns. Hydrostatic head graphs suggested the addition of 2% FRG-1 could raise this barrier property from 200 to 700mms when starting with a 35 MFI PP at 275C and 0.6g/h/m. (Air permeability fell from 1 to 0.36 m/s)

Using the additive on line to reduce the viscosity of a spunbond grade to that of a melt-blowing grade was said to offer cost-savings compared with the use of conventional melt-blown polymers. Waste reprocessing is improved. Furthermore, the system has no safety problems according to cytotoxicity, skin irritation and sensitisation testing.

FRG-2 was mentioned as a much faster acting degrader which appeared to be based on peroxides.

Fiber diameter in Melt-blowing

Dr Randall Bresee of the University of Tennessee considered the factors which determine fiber diameter development during melt-blowing:

• The air velocity at the die tip causes uniform draw.
• As the air-flow becomes turbulent irregular draw occurs as still-plastic fibers collide
• If filaments stick together in the turbulence, diameter increases
• Web shrinkage at the collector increases diameter.

The mean fiber diameter continues to fall even 20-80 cms from the die and this must be due to effect 2, but the maximum fiber diameter also increases so this has to be due to effect 3. The increasing variability of fiber diameter can also be measured in the same region. As the air flow at the die tip increases up to 550 cuft/min, the diameter falls, but above this flow it increases for a given die-collector distance. An interaction with DCD means that this optimum flow increases as DCD increases.

Overall, fiber diameter seemed to be affected significantly by die temperature, moderately by resin throughput rate and primary airflow rate, slightly by DCD, and insignificantly by collector speed. As DCD was increased, mean fiber diameter decreased and fiber diameter distributions shifted to finer fibers but the maximum fiber diameter and diameter CV increased. Fiber diameters became significantly less uniform when primary airflow rate was increased, especially when DCD was large. This result was viewed as evidence that diameter reduction occurred by fiber contact/entanglement when DCD was increased.

Dr Bresee thought that fiber diameter variation across the web would almost certainly be due to die temperature variations. Asked if the effects of air temperature had been studied, they hadn't but Dr Bresee thought that air temperature would be the same as the die temperature.

Patterning Nonwovens

Alan Meierhoefer (Consultant) focused on techniques which rearranged the fibers in a web rather than simply printed or embossed bonded structures. Patterning made nonwovens more textile-like, improved some physical property or offered branding possibilities. This could be done before, during or after bonding the web. The water marking techniques of the speciality paper industry used patterned or knuckled wires which encouraged short fibers to congregate in the “valleys” and form a mirror-image of the wire pattern. Hydroentanglement achieved the same effect after web forming with high pressure water jets forcing longer fibers to move into the valleys, or into the holes of perforated collection plates. Higher water pressure still could be applied to the surface of bonded webs through patterened screens to modify the structure of a bonded nonwoven, this being the best way to add logos to hydroentangled fabrics. Examples given were perforated tea-bag papers with company logos, the original J-cloth wipes from Chicopee and the Miratec or Apex technology from Chicopee which PGI used to make textile like nonwovens. The latter used deeply 3D forming zones and could mimic most textile weaves. The original pyramid Apex pattern actually twisted the fibers together as they were washed down the sides of the pyramid by the high pressure water.

Asked why these techniques had had little success replacing woven textiles, Dr Meierhoefer said the fabrics lacked durability to abrasion and probably cost more to make than imported wovens.

3D Nonwovens

Carol Clemens, the Director of Business Development for Freudenberg introduced Novolon™. Whilst this looked like a deeply embossed nonwoven (or fibrous version of bubble- wrap film) she was at pains to point out that conventional embossing would puncture the nonwoven if depths achieved with Novolon ™ were attempted. The key to Novolon™ was the use of unoriented thermoplastic fibers which could stretch by 200-300% when deeply embossed, the fibers being oriented and set in the process. Fibers with all deniers and shapes, bicomponent or otherwise would work in the process provided the webs were random laid. Crimp was desirable. Technical data for Evolon™ and spunbond fabrics showed that the spunbond gave dramatically higher compression resistance, especially when two layers of the moulded sheet were combined either with the domes “nested” or glued dome to dome. Here the use of twice the nonwoven gave treble-quadruple the compression resistance.

Freudenberg were targeting the foam market with these products, presumably the rigid foam market in view of the likely low resilience of Novolon™. Advantages over foam were listed as:

• Very high water/air permeability
• No water absorption
• Could use half the weight (c.f. foam) to achieve a given resistance to compression
• Lower flammability
• Recyclable
• 1000 times the tear strength of the equivalent foam.
• Quick drying
• Aesthetically pleasing texture and appearance.

On the other hand it was more expensive than foam, could not easily be shaped and could not easily be made very thick. Markets under development were acoustic and thermal insulation panels, filters, upholstery and automotive padding and concrete reinforcement.

In response to questions, Freudenberg had licensed the process from NC State University, having supported its development. Thermal bonded nonwovens could not be used because they punctured. Lightly hydroentangled, needled or spunbonded webs were best. Blends of up to 50% with cellulosics could be processed. The line runs at 50 m/min with basic spunbond but has to slow down for coarser fibers. The depth of embossing is limited by the extensibility of the fibers in the web – currently 50mm with undrawn synthetics.

Coloring Nonwovens

Dr Dick Aspland of Clemson reviewed textile dyeing and finishing technology with special emphasis on its application to nonwovens. Dyeing uses colored chemicals in solution, the uptake of which by fibers depends crucially on the fiber forming conditions and their thermal/chemical history. Different fibers need different dye-types and the process of dyeing is often at done slowly at elevated temperatures with vigorous agitation of the fabric. In short it's next to impossible to dye nonwovens to uniform shades without adversely affecting the structure.

Pigments can be added to the fiber forming polymer – erroneously known as dope-dyeing, and pigments can be bonded to the surface of a nonwoven (“printing”). Here there are pigment penetration issues, wicking effects, migration of pigment and the removal of additives from the nonwoven to contend with, and the pigment binders need heat curing. Transfer printing using heat to sublime disperse dyes from a printed paper on to the nonwoven is possible at temperatures of around 350F but this is probably too hot for most nonwovens.

Asked if he was aware of any further research being carried out to improve nonwovens coloration, Dr Aspland thought not. The whole subject was just too complex and uniquely dependent on the wide and variable range of nonwoven constructions.

Printing with aqueous inks

Steven Dalbey, of Polytex Environmtal Inks thought gravure and flexographic printing techniques work well with nonwovens while the offset litho and silk screen methods were good but too expensive. Gravure uses a single roller etched with the mirror-image of the pattern to be printed. The ink or pigment is “doctored” into the etching on one side of the roll and the fabric is squeezed against the other side to pick up the color. Flexography is similar but the ink-pattern is transferred to a second smooth roller and from there to the fabric. Flexography runs fastest and can easily be retrofitted to a nonwoven production or conversion line. (“easily” applies to single color printing, the complexity increasing as the color range increases.) Nowadays, inks can be water-based and applied from sealed “doctor chambers” to allow a system with easy clean-up, and negligible liquid effluents or hazardous air pollution. Such systems are in use on baby products, medical nonwovens, food service wipes and are proving invaluable as a means of differentiating your product. Mr Dalbey said that printed diapers could be recognized by toddlers who now begged Mum to buy their favorite designs. Prints can also affect perception of performance, identical products being judged to perform very differently if the user liked or disliked the printing (in this case of the packaging)

“Inks” which add functionality such as extra absorbency, odor control, odor, hydrophilicity or which can add special effects such as differential drainage were now possible. For instance a topsheet could be printed invisibly on the diaper line with both hydrophobic and hydrophilic inks to localise strikethrough into predetermined regions.

In response to questions, any polymer could be printed with aqueous inks once the correct binder had been identified, and different fabric types (e.g. HE, SB, MB) could be printed to the same color by adjusting the inks. For baby wipes, the lotion formulation would affect the choice of ink for acceptable color fastness.

Perception of Whiteness

Dr. Mary Ann Moore of Florida State University said whiteness was a key factor in consumer perception of a product and the texture of that product will affect the apparent whiteness. Whiteness, being the absence of color, communicates a purity and freedom from contamination to the user, and surfaces appear whiter the more uniformly smooth they are. She provided data from CIE Lab assessments of nonwovens where the ‘L' value measures the greyness of a fabric (0=black, 100=white), the ‘a' value the red-green balance (with zero being neutral, -ve values green and +ve values red), and the ‘b' value measures the blue-yellow balance ( with zero being neutral, -ve values being blue and +ve values yellow)

The data provided did not really illustrate the main theme but a comparison of 16 spunbonds with 7 meltblowns yielded the following conclusions:

• Meltblowns appeared (to the CIE Lab instruments) whiter, greener and yellowier than the spunbonds.
• Higher bonding temperatures gave whiter, bluer nonwovens
• Higher bonding pressures gave greener fabrics.

Unfortunately the melt-blown and the spunbond had been made from different polymers, so the main conclusion to be drawn was that Florida SU could measure whiteness on a wide range of nonwovens and were looking for support to do a proper study.

Pigment Printing

Barry Byrd of BASF reported how pigment printing of color-fast finishes has improved:

• Compatiblizers now keep the emulsions in better condition
• Application is more uniform
• Clean-up is easier
• Migration is more under control
• There is a better understanding of how ambient temperature and pH affects the process.
• Wide-width padding or foaming techniques work well.
• Masterbatches are now prepared with everything but color and color is added last in a small header tank close to application.

An initial pre-dry where the temperature is rapidly raised to above 125F is needed to fix the pigment before normal drying and curing. No after washes are needed so there is no effluent. Resination is possible in the same bath and color fastnesses are excellent. Superfine powder pigments are becoming available and these can penetrate the fiber structure.

Barrier Coating

Melanie Jones of Precision Fabrics Group Inc described the new AAMI Standard PB70:2003 which guides health care workers to choose the appropriate level of protection. Garments must be labelled to indicate the level of protection offered on a scale of 1-4.

Level 1 must pass the AATCC42 water impact penetration test with a level of penetration below 4.5 gms.

For Level 2 the penetration must be less than 1 gm, and the fabric must also pass AATCC127 with a hydrostatic head better than 20 cms.

Level 3 is as for Level 2 but with the hydrohead standard increased to better than 50 cms.

Level 4 is based on two completely different tests. ASTM F1671, a microbial assay of viral pass through, and ASTM F1670, a blood barrier test.

Coatings which can be used to meet these standards include fluorochemicals which repel both water and alcohol but are expensive, or waxes which repel water and are cheap but not durable. Foam coating of fluorochemicals is needed to meet the highest standards.

Passing Level 4 Barrier standards?

Larry Wadsworth of the University of Tennessee introduced the thermally bonded tri-laminate , a combination of his “Cotton Surfaced Nonwoven” ( a PP spunbond with a cotton/PP blend thermally bonded to one surface) and Noveon™ monolithic barrier film. The CSN layers were coated with various fluorochemicals and antimicrobial latexes both before and after lamination to the film. Numerous variations on this theme had been evaluated against the new Level 4 barrier standard (above). Most could pass the blood-barrier test but failed the viral penetration test. The film coated tri-laminates, which were first foam coated with fluorochemical on the outer spunbond side and with antimicrobial latex on the cotton side passed ASTM 1670, and had a virtually 100% kill rate to bacteria. Some of these complex constructions also passed the viral barrier test. The work is supported by Cotton Incorporated.

Flame Barriers

Ron Dombrowski of TechTex Solutions Inc has compared nonwovens with wovens as flame barriers and finds that needled nonwovens give longer flame hold-out times than wovens of the same weight and chemistry. Interestingly on his test there was no difference between FR treated cotton or rayon (cheap and relatively comfortable) and Nomex (expensive and uncomfortable). It is of course the bulk of the nonwoven that makes the difference; if they are compressed to the same thickness as wovens the performance is the same. What FR agents were used on the cellulose? The usual phosphorous/halide-containing chemicals.

Demique® Nonwovens

Atul Dahiya of the University of Tennessee Knoxville described their work with the Kimberly-Clark melt-blown elastomer process. K-C had intended to use this process for diaper components but had found it too expensive and had donated the technology to UTK for further work. The Arnitel EM400 copolyether-ester resin had been subjected to a full factorial experiment to identify the main effects and interactions of die temperature, throughput, and die/collector distance. Highest tear strengths came from low die temperature and high DCD while highest elongations came from high die temperature and low DCD. (Student presentation – paper not available)

Modelling Water Flow in HE Nozzles

Nagendra Anantharamalah of North Carolina State University has obtained excellent correlation between the computer model and the observed performance of a single nozzle over a range of water pressures. Best water column integrity is obtained when a hydraulic flip occurs and the water passes through the nozzle without touching the sides. This is achieved only with cone-down nozzle arrangements. Cone-up trials gave 50% higher discharge coefficients. (Student presentation – no paper available. The same data was presented at INTC in 2003 and is fully covered in that summary)

Multiple On-Line Measurement

Michael Cunningham of EGS Gauging Inc reviewed the methods available for continuous on-line measurement of fabric properties. Infra-Red was preferable to beta, gamma, laser or X-ray. Ratiometric beamsplitter IR – which could quantify a component of the web by measuring the peak-to-background difference in IR absorption at a single wavelength was good but pigments or additives caused problems and any change of fiber needed “weeks” for recalibration and software upgrades. The latest single-sensor Full Spectrum IR gets round these issues and allows calibration for a variety of components with and without pigments. This uses an online spectrophotometer which can assess multiple components in the web including fiber blend ratio, pulp content, water content, binder content and basis weight. Users of this system report significant cost savings from 3-5% raw material savings, and 60-70% reductions in MD and TD property variability.

Value Added Printing

Kevin Marrick of PCMC covered the variety of ink types and curing technologies, arguing that water-based – which need more drying but are simple to use and free of VOC's - is the way forward for nonwovens . They are usually emulsions and require coalescents to soften the polymer binder and enhance its ability to fuse on curing. The use of expandable polymers allows the creation of texture for improved wiping, or exfoliation. They are applied from Anilox rolls comprising a steel core with a ceramic coat, laser engraved with the required pattern, to a depth to get the required capacity. Ink capacities are measured in BCM's – Billion Cubic Microns. The engraved plates can be in the form of sleeves, and the surfaces need continual cleaning to remove any fiber or residual ink. Drying needs to occur very quickly and with water-based inks the required time, temperature and turbulence are hard to achieve for high speed processes where more than one color is applied. Compressed air at supersonic speeds is used. Asked about coverage, Mr Marrick said solid colors could be obtained with the system. He could not share information on the costs of the process and inks.

Surface Modified Films

Vasantha Datla of NC State has investigated the effect of melt additive chemistry on the hydrophobicity of polypropylene using 4 different groups of additives:

• Nonyl Phenol Ethoxylates,
• POE(n)-Stearyl Alcohol,
• Melt additives with C18 chain but different hydrophilic group, and
• Melt additives with similar hydrophilic-lipophilic balance (HLB), but different molecular sizes.

The conclusions were as follows:

• Melt additives concentrate at the film surface (proved using X-ray photo-electron spectroscopy).
• Melt additive migration leads to a hydrophilic surface by reducing the water contact angle over several days following fiber extrusion.
• Smaller molecular size and lower HLB leads to immediate melt additive enrichment yielding extra oxygen at the surface by day 2.
• Additional migration occurred between day 2 and Week 3 for most melt additives.
• Soaking the films in water changes surface properties further to an extent dependent on the type of the melt additive and the immersion time.

Asked if the conclusions would be valid for fibers, Mr Datla confirmed they would. He has yet to check the levels of surfactant in the water in which the films were soaked but agreed that the additive would probably be leaching out. Effects of additive concentration and the temperature during migration remain to be studied.

Fiber wetting and absorbtion?

You-lo Hsieh of UCal (Davis) described the measurement of liquid wetting and absorption on several nonwoven materials with different manufacturing methods and

fiber contents, and on ultra-fine fibers generated by electrospinning of polymer solutions. The identified nonwovens were 2 filter papers (glass and aramid) and 2 hydroentangled cotton fabrics. The nanofibers were electro-spun from cellulose acetate in acetone and dimethylacetamide mixtures and were deacetylated to varying degrees of substitution down (down to 0, or pure cellulose) using caustic soda. He has also studied the effects of grafting “polymer brushes and gels” for controlled release and “stimuli-responsive” properties.

Modelling the Schwarz Melt Blowing Die

Holly Krutka of the University of Oklahoma has simulated 6 different multi-hole die geometries in 3 dimensions, calibrating the simulation against experimental results in the published literature. The flow fields from the multi-hole simulation were very different from the earlier single hole simulations. Velocity maxima occurred closer to the die face and the spreading rates for air jets in the center of the array was much less than for a single jet. Orifice spacing was shown to have a significant effect on the interaction between inner and outer jets. (The Schwarz die has a hot air “sheath” around each die hole rather than the air knife slot across the entire die width)

Improving Appearance and Texture

Roy Bamford of Aurora Textiles Finishing Co reviewed the multiplicity of mechanical and chemical methods used by textile manufacturers to affect the look and feel of durable fabrics. The only “new” process mentioned was a softening machine which used beaded rolls to “massage” the fabric against soft rubber to locally stretch and soften. This could be an alternative to compressive shrinking (Micrex) which was also mentioned.

Basis Weight Uniformity Studies

Dr Randall Bresee of the University of Tennessee showed how automatic optical scanning of a nonwoven on a light table could yield detailed information on the basis weight uniformity. The instrument scans a large full-width sample and uses different “pixel” sizes to generate a “uniformity spectrum”. Images are acquired from a 640x480 8-bit monochrome (256 gray levels) camera using autofocus but fixed aperture and exposure time. Uniformity is expressed as the CV% for different areas ranging from the 40 micron square individual pixels up to the 25mm square “whole images”. A plot of CV% versus area viewed provides the unique uniformity spectrum for that sample. Data can be analysed to separate out MD and CD variations.

Determining Web Uniformity

Dr Behnam Pourdeyhimi of NCRC appeared to be using a similar optical technique to Dr Bresee to characterize a 400 cm 2 sample in 400 x 1cm 2 regions and used the Poisson test to determine the spatial uniformity of the images obtained. The “quadrant” method was used to divide the sample into n=4, 9, 16….equal squares and the variance for each value of n could be calculated along with the dispersion index and the chi-square value. A uniformity index was then obtained. ( Unfortunately neither the presentation nor the written paper allowed more clarity than this. The conclusions, reproduced here in full, were as follows: “The findings of this current study indicate that appropriate strategies can be developed to characterize nonwoven fabrics”.)

Spunbond Uniformity/Permeability Relationships

Dr Rita Salvado of the Universidade da Beira Interior ( Portugal ) has studied the visual uniformity of a large number of spunbond nonwovens and compared it with air permeability measurements. As expected the more uniform the fabric the lower the air permeability. The standard deviations of the air permeability results were observed to correlate well with the apparent uniformity, so Dr Salvado proposed the use of air permeability variation as a measure of fabric uniformity.

Calvin Woodings

29 th September 2005